Equivalent is called the particle which is chemically equivalent (is equivalent) in the acid and main reactions to one ion of hydrogen, and in reactions of oxidation-reduction type - to one electron. The equivalent is expressed by number without dimension whereas equivalent weight is measured in g/mol.
It is required to you
- - calculator;
- - periodic table
Instruction
1. That it was possible to find an equivalent of any given substance, you have to use a formula: 1/z (some substance), where 1/z – a factor of equivalence (fe), that is number which shows what share of a particle of substance is equivalent to an equivalent. This size is always less or is equal to unit. In other words, the factor of equivalence is a certain coefficient which registers just before a substance formula when finding an equivalent. For example, you should find an equivalent of phosphoric acid in its interaction with sodium hydroxide. Write down the reaction equation: 2NaOH + H3PO4 = Na2HPO4 + 2N2OOtsyuda is visible that on atoms of sodium only two atoms of hydrogen are replaced, that is acid is dibasic (2 ions of H+ participate in reaction). Thus, according to definition, the conditional particle of ½ H3PO4 will be an equivalent of phosphoric acid.
2. Consider that the equivalent of the same substance changes in dependence of type of reaction which this substance enters. Besides, the equivalent of an element is depending on a type of connection which part is. Take the same substances, as in the previous case, but reaction let will go in a different way: 3NaOH + H3PO4 = Na 3PO4 + 3N2O.Zdes fэ(H3PO4) = 1/3, fe (NaOH) =1. Therefore, the equivalent of phosphoric acid - a particle 1/3 H3PO4, and an equivalent of alkali is equal to unit.
3. For successful finding of equivalents of various substances you need to remember formulas for finding of fe depending on type of chemical compound. So for the simple fe elements = 1/valency of an element. Example: fe (H2SO4) = 1/6, and a sulfur equivalent is equal in H2SO4 to 6. For salts - fe = 1/n (mt.) - B (mt.) = 1/n (to. the lake) - B (to. the lake), gden (mt.) – amount of atoms of metal, B (mt.) – the valency of metal, n (to. the lake) – quantity of the acid remains, B (to. the lake) - the valency of the acid rest, etc.
4. It is more difficult to find a substance equivalent in reactions of oxidation-reduction type as you will conduct calculation for number of electrons which take part in process of restoration or oxidation. The task to find a manganese hydroxide equivalent in reaction is given: 2Mn + 12NaOH + 5Cl2 = 2NaMnO4 + 10NaCl + 8N2OIz the equations it is visible (OH)2 that manganese gives 5 electrons and passes from Mn +2 into Mn +7. Means, the factor of equivalence of Mn (OH) 2 - 1/5, and an equivalent of hydroxide is equal to 5.